DE19802846A1 - Manually and automatically operated braking force amplifier or main cylinder unit with defined manual actuator element rest position - Google Patents

Abstract

The unit has a pneumatic braking force amplifier with an amplifier housing divided internally into a vacuum chamber and a working chamber by at least one movable wall. A control valve that controls the pneumatic pressure difference acting on the wall can be independently actuated by a manual input element or electromagnet arrangement. A hydraulic main cylinder (14) coupled to the amplifier receives the actuation force input to the amplifier and the servo force generated by it via an input piston connected to the actuating piston, which is coupled to the mechanical input element, and to the control valve housing and extending into a first main cylinder pressure chamber. A telescopic auxiliary housing (34) is connected to the movable wall (22) so as to transfer force. A second input piston (46) has a force transfer connection to the auxiliary housing. The first input piston (44) is spring biassed towards the actuating piston (42).

Description

The invention relates to a brake booster / master cylinder Unit according to the preamble of claim 1. The in the Brake booster containing such units electric magnet arrangement offers the possibility of the brake system of the Vehicle in which such a unit is installed, too to operate independently of the driver's will or the driver's will suitable to support. In this way, the Brake systems of modern cars with additional functions verse hen. As an example of these additional functions, here are the traction control, the driving dynamics control (also as Stability program), an automatic distance re successful, and finally called the so-called brake assistant, automatically as soon as possible when emergency braking is detected provides the maximum braking force support.

With previously known brake booster / master cylinder Units with additional electromagnetic actuation poss there is the problem that with an automatic Braking, d. H. with a regardless of the driver's will the electromagnet arrangement braking, z. B. in As part of a vehicle dynamics control (electronic stability programm) or an automatic distance control, the brake pedal out of its rest position, which is in the unactuated position Condition of the brake system is in the direction of actuation moves. The driver who with his foot in at such a moment the brake pedal will not find the brake more in the usual place, what can unsettle him and is therefore undesirable.

The Bremspe is already known from the prior art dal to decouple during an automatic braking process, so that it remains in its rest position. With one However, the solution to the problem arises that a driver who during an automatic braking process from any  Want to intervene in the braking, the brake pedal initially through a possibly considerable free travel must move before the brake pedal gives him the usual feeling of braking mediated. Such a failing brake pedal will usually associated with a defect in the braking system and can therefore be a highly undesirable driver Trigger panic reaction.

The invention has for its object a Bremskraftver stronger / master cylinder unit with manual and automatic, for example electromagnetic actuation To provide, in which the manual actuator, at for example a brake pedal, while an exclusively car automatic actuation of the unit in a single, defined Rest position remains out of the without a noticeable An additional free travel of the manual actuator manual braking can be made.

This object is according to the invention with a brake booster ker / master cylinder unit solved, which in claim 1 Features specified.

According to the invention, the control valve housing of the pneuma table brake booster with an additional auxiliary ge provided the telescopic with respect to the Control valve housing is slidable and preferably on the Control valve housing is arranged. With this auxiliary housing is the movable wall of the pneumatic brake booster connected to transmit power. In addition to a first one gear piston, also in known brake booster / main cylinder units is present, the inventive Brake booster / master cylinder unit a second one gear piston, the power transmission with the auxiliary housing is connected and the same as the first input piston to into a first pressure chamber of the hydraulic master cylinder enough. Is advantageous for power transmission from the Hilfsge housing on the second input piston facing the latter End face of the auxiliary housing used. The first input piston  the brake booster / master cylinder according to the invention Unit is resilient towards the in the control valve arranged actuating piston biased.

Because of this constructive design moves at an automatic actuation of the unit the auxiliary housing together with the movable wall towards the head cylinder without moving the (main) control valve housing becomes. The movable wall of the brake booster can Force resulting from the pressure difference applied to it results in the auxiliary housing and the power transmission with it connected second input piston into the first pressure chamber of the Master cylinder transmitted and through the stroke of the second one correspond to the hydraulic pressure in this pressure chamber increase accordingly. Since the first input piston moves during a automatic actuation does not move, manual remains Actuator (e.g. a brake pedal) of the invention Brake booster / master cylinder unit in its output or rest position.

Because also the first input piston in the first pressure chamber of the master cylinder ends and thus that in this pressure chamber prevailing hydraulic pressure always on the first input piston acts, and because the first input piston is resilient in Direction on the actuating piston of the control valve is tensioned with one end of the mechanical input member is already in the rest position of the manual Actuator connected to the other end of the mechanical Input element is coupled, which is currently in the master cylinder prevailing hydraulic pressure to the manual actuator reported back. A driver therefore feels when actuated of the brake pedal without loss of the actual braking appropriate feedback force and can brake in the usual way Way z. B. increase dosed.

According to a preferred embodiment of the invention The brake booster / master cylinder unit surrounds the second Input piston concentrically concentrates the first input piston, d. H. of the  second input piston is designed as a hollow piston. At a such an embodiment, the resilient preload is advantageous of the first input piston in the direction of the actuator supply piston of the control valve through the first input piston and pushing apart the second input piston Spring generated.

The first input piston particularly preferably couples in actuation direction after walking a predetermined path with the second input piston. This is how they behave apart from both input pistons for manual actuation from an initial phase like a single input piston. Con The first input piston is structurally advantageous as Plunger formed, the sealing and slidable in the arranged as a hollow piston second input piston is.

In advantageous embodiments of the brake according to the invention power amplifier / master cylinder unit serves the end face of the Control valve housing the first input piston as a stop in Opposite direction of actuation. For example, the through knife of the first input piston at its the control valve end facing the housing must be larger than the diameter of the interacting with it, arranged in the control valve housing Actuating piston.

In preferred configurations, the auxiliary housing is supplied turned end of the second input piston adjustable in length educated. The said end of the second input piston can for this purpose, for example, be provided with an external thread that an adjustment ring is screwed on the face of the auxiliary housing. By more or less strong The adjusting ring can then be screwed onto the external thread the axial position of the second input piston with respect to the Auxiliary housing can be set. Such an adjustment possible It makes it easier to compensate for manufacturing tolerances and every brake booster / master cylinder unit in a series to give the same characteristic.

An embodiment of a Bremskraftver invention stronger / master cylinder unit is shown below using the attached, schematic drawings explained in more detail. It shows:

Fig. 1 shows the area of interest of a brake booster / master cylinder unit according to the invention in longitudinal section, Fig. 1 showing the standby position, ie the unactuated state, and

Fig. 2 shows the view of Fig. 1 in an electromagnetically actuated state, ie during an automatic braking.

Fig. 1 shows a longitudinal section through the mainly interesting part of a brake booster / master cylinder unit 10 for a hydraulic brake system of a motor vehicle, which consists of a pneumatic brake booster 12 and a flange-mounted hydraulic master cylinder 14 .

The brake booster has an amplifier housing 16 , of which only a part is shown in FIG. 1. The amplifier housing 16 is formed from two sheet metal half-shells 18 , 20 and delimits an interior space which is divided by a movable wall 22 into a vacuum chamber 24 and a working chamber 26 .

In the amplifier housing 16 extends along an axis A, a control valve 28 for controlling a pneumatic pressure difference acting on the movable wall 22 . The control valve 28 has a here made of two rigidly connected parts 30 , 32 existing control valve housing, which is slidably and sealingly received in an axially outward, cylindrical neck of the amplifier housing 16 and which expands in a step-like manner in the amplifier housing 16 .

On the larger diameter section of the control valve housing 30 , 32 there is an essentially pot-shaped auxiliary housing 34 which is axially displaceable relative to the control valve housing on the latter and which has a circumferential radial flange 36 on the outside, to which the movable wall 22 is fastened in a sealing and force-transmitting manner. A arranged in the Unterdruckkam mer 24 , supported on the master cylinder 14 return spring 38 biases the control valve housing together with the movable wall 22 in the output position shown in Fig. 1 before.

The control valve 28 and thus the brake booster 12 can be actuated with a rod-shaped here, axially projecting axially into the control valve housing, mechanical input member 40 , which acts with one end in the control valve 28 on an actuating piston ben 42 and the other end of which, for example, with a brake pedal, not shown connected is. The actuating piston 42 transmits the actuating force introduced by the input member 40 to a first input piston 44 of the master cylinder 14 attached to the vacuum-side booster half 18 .

The first input piston 44 embodied here as a plunger piston is concentrically surrounded by a second input piston 46 which is hollow throughout. Both input pistons 44 , 46 end in a first pressure chamber 48 of the master cylinder 14 and are exposed to the hydraulic pressure prevailing there. A helical compression spring 50 is accommodated in the largest part of the diameter of the through bore of the second input piston 46 , the one end of which is supported on a step of the aforementioned through bore and the other end of which is supported on a radial flange 52 of the first input piston 44 . The helical compression spring 50 thus urges the two input pistons 44 , 46 axially apart and thereby tensions the first input piston 44 against the end face of the control valve housing part 32 facing it or against the actuating piston ben 42 . The fitting in Fig. 1 on the actuating piston 42 end portion of the first input piston 44 has a larger diameter than the actuating piston 42, so that the first input piston 44 when building up 48 hydraulic pressure in the first pressure chamber, without the input member 40 applied a corresponding counterforce is in contact with the end wall of the control valve housing part 32 in order to be supported thereon.

In the area of its opposite end, the first A piston 44 is provided with two further radial flanges 54 , 54 ', between which a sealing ring 55 is received. When the brake booster / master cylinder unit 10 is actuated manually via the mechanical input member 40 , the first input piston 44 couples with the second input piston 46 against the force of the helical compression spring 50 after passing a short distance in the actuation direction, by the radial flange 54 against a step 56 pushes, which is formed in the through bore of the second input piston 46 by a further diameter narrowing. The two input pistons 44 and 46 are then moved together with each other into the first pressure chamber 48 with continued pressure on the input member 40 and behave like a single piston.

An end portion of the second input piston 46 facing the auxiliary housing 34 is provided on the outside with a thread 57 onto which an adjusting ring 58 is screwed, which rests on the end face of the auxiliary housing 34 . The adjusting ring 58 , on the axially opposite side of which the return spring 38 is supported, serves on the one hand to transmit power between the auxiliary housing 34 and the second input piston 46 and on the other hand to adjust the length of the second input piston 46 . By screwing the adjusting ring 58 more or less far onto the external thread 57 , axial manufacturing tolerances can be compensated for between the mechanical input member 40 , the actuating piston 42 , and the master cylinder 14 .

On the actuating piston 42 , a first, annular valve seat 59 is formed, which cooperates with a first, circular annular disk-shaped valve member 60 and which, in the open state, connects the working chamber 26 to atmospheric pressure (or overpressure) via a radial channel 62, which pressure from the outside through an inlet opening 64 can flow into the control valve housing. Through the radial channel 62 of the control valve housing protrudes a fixed to the actuating piston 42 Querrie gel 66 , the axial relative movement of the actuating piston 42 relative to the control valve housing by coming into contact with the left side wall of the channel 62 in the Figu ren limited upon actuation of the control valve 28 and the upon a return movement of the actuating piston 42 at the end of a braking operation against a stop 68 formed in the half-shell 20 of the amplifier housing 10 , which defines the so-called release position (unactuated position) of the brake booster 12 .

For automatic, ie independent of the driver's actuation of the brake booster, the control valve 28 has an electromagnet arrangement 70 , which is taken up in the section of larger diameter of part 30 of the control valve housing and which has a hollow cylindrical armature 72 , a coil housing 74 and one accommodated therein , from a coil holder 76 carried coil 78 which surrounds the armature 72 ringför mig. The electromagnet arrangement 70 is arranged coaxially with the actuating piston 42 and is pushed through by the latter. Radially between the armature 72 and the coil housing 74 or the coil holder 76 is a thin-walled separating sleeve 80 made of non-magnetic material, on the inner surface of which the armature 72 can slide axially.

The armature 72 is rigidly connected, for example by screwing, to a hollow cylindrical actuating sleeve 82 which coaxially surrounds the actuating piston 42 and extends out of the electromagnet arrangement 70 in the direction of the input member 40 . Outside the electromagnet arrangement 70 , the actuating sleeve 82 has a radial flange to which a plurality of arms 84 , which extend essentially parallel to the axis A in the direction of the first valve member 60 , are fastened, of which only one can be seen in the figures. The arms 84 end in the state shown in FIG. 1 (unactuated solenoid arrangement 70 and no actuation of the input member 40 ) radially outside the first valve seat 59 axially shortly before the first valve member 60 .

At a position corresponding axially to the first valve seat 60 in relation to the rest position shown in FIG. 1, on the inside of the control valve housing part 30 radially outside the first valve seat 59 and the arms 84 there is a concentric with the first valve seat 59 , also annular and cooperating with the first valve member 60 forms second valve seat 86 , which can connect the vacuum chamber 24 to the working chamber 26 in the open state via an annular channel 88 .

The provided with a rubber-elastic pad member 60 is pressed by a first compression spring 90 in sealing contact with the first valve seat 59 and the second valve seat 86 , the valve member 60 at one end and the other end at one end annular insert 92 supports. A second compression spring 94 , also supported at one end on the insert 92 , the function of which will be explained below, presses an annular spring adjuster 96 axially against a stop 98 formed on the inside of the control valve housing part 30 . The second compression spring 94 can have a greater spring force than the first compression spring 90 .

A conical spring 100 , which is supported on the side opposite the compression springs 90 , 94 of the insert arranged sealingly in the control valve housing part 30 , the other end of which is supported on a step of the input member 40 , prestresses the latter against the direction of actuation.

Seen from the input member 40 axially beyond the Elek tromagnetanordnung 70 on the part 32 of the control valve housing, a third annular valve seat 102 is formed, which cooperates with a second valve member 104 similar to the first valve member 60 and which together with the second valve seat 86 the Controls connection between the vacuum chamber 24 and the working chamber 26 . The third valve seat 102 has, at least approximately, the same sealing diameter as the second valve seat 86 .

An annular fourth valve seat 108 is formed on the electromagnet arrangement 70 by a short axial and annular circumferential collar 106 of the coil housing 74 , the sealing diameter of which corresponds to that of the third valve seat 102 and which also interacts with the second valve member 104 . In the output or rest position of the control valve 28 shown in FIG. 1, the second valve member 104 is pretensioned by a third compression spring 110 in contact with the fourth valve seat 108 , ie the third valve seat 102 is open in the rest position of the control valve 28 .

The entire electromagnet assembly 70 is mounted in the Steuererventilgehäu se 30 , 32 axially floating between the second valve member 104 and a fixed, annular stop 112 against which the coil housing 74 of the electromagnet assembly 70 is pressed in the rest position of the control valve 28 due to the resilient bias of the second valve member 104 becomes. The housing-fixed stop 112 is provided with an elastic sealing bead 114 in order to be able to seal against the coil housing 74 .

The function of the brake booster / master cylinder unit 10 will now be explained in more detail with reference to the figures. If a driver actuates the brake pedal, not shown here, the input member 40 and the actuating piston 42 move from their rest position shown in FIG. 1 relative to the control valve housing 30 , 32 in the direction of the master cylinder 14 , that is to say to the left in the figures. As a result of this displacement, the first valve seat 59 is lifted off the first valve member 60 , so that atmospheric pressure can flow from the outside through the air filter element 64 past the first valve seat 59 and through the radial channel 62 into the working chamber 26 . A differential pressure then builds up on the movable wall 22 , which displaces the wall 22 and the control valve housing 30 , 32 together with the auxiliary housing 34 to the left. The corresponding servo force is delivered via the end face of the control valve housing part 32 and further via the first input piston 44 and via the end face of the auxiliary housing 34 and further via the second input piston 46 to the master cylinder 14 .

After releasing the brake pedal, the conical spring 100 presses the input member 40 relative to the control valve housing 30 , 32 against the operating direction, ie to the right in the figures. The first valve seat 59 comes back in sealing contact with the first valve member 60 and opens this movement against the force of the first compression spring 90, the second valve seat 86 , which due to the also open third valve seat 102, the connection between the vacuum chamber 24 and the working chamber 26 is open. Because the vacuum chamber 24 is constantly connected to a vacuum source, for example with the intake tract of an internal combustion engine, the differential pressure applied to the movable wall 22 is reduced with a corresponding reduction in the servo force output by the brake booster 12 .

The above functional description relates to a manual actuation of the brake booster 12 taking place by means of the input member 40 . In the case of electromagnetic actuation, a connected to the brake booster 12 and not shown electronic control unit excites the coil 78 of the electromagnet assembly 70 with a certain current which corresponds to the desired servo force to be output by the brake booster 12 . A magnetic field then builds up in the electromagnet arrangement 70 , which pulls the armature 72 to the right until the arms 84 of the actuating sleeve 82 firmly connected to the armature 72 abut the first valve member 60 . Due to the resistance opposed by the first compression spring 90 biased valve member 60 , the floating spool 74 then pushes ver 74 of the electromagnet assembly 70 in the opposite direction, ie to the left, and presses the second valve member 104 against the force of the compared first compression spring 90 weaker third compression spring 110 in sealing contact with the third valve seat 102 .

The armature 72 and the actuating sleeve 82 rigidly connected to it then resume their previously interrupted movement to the right, as a result of which the first valve member 60 to the right initially only against the force of the first compression spring 90 and, after the stop against the spring plate 96 , also against the force the second compression spring 94 is displaced and is thereby lifted off the first valve seat 59 . From a so-called control position, the electromagnet arrangement 70 thus never works against a steeper spring characteristic, which is advantageous from the point of view of control technology because of the lower control effort thereby achieved. The second valve seat 86 is also open in this state, however, the third valve seat 102 is closed as mentioned above, so that there is no connection between the vacuum chamber 24 and the working chamber 26 . Rather, as described in connection with the manual actuation, atmospheric pressure is supplied to the working chamber 26 through the opened first valve seat 59 and, as a result, the movable wall 22 is displaced.

This displacement of the movable wall 22 is transmitted via the Ra dial flange 36 only to the auxiliary housing 34 , which then moves relative to the control valve housing 30 , 32 telescopically in the direction of the master cylinder 14 , whereby it over its end face and the adjuster ring 58th takes the second input piston 46 ( Fig. 2). The second input piston 46 is accordingly shifted according to the displacement of the auxiliary housing 34 into the first pressure chamber 48 of the Hauptzy cylinder 14 and there generates a correspondingly increased hydraulic pressure. This hydraulic pressure also acts on the end face of the first input piston 44 , which thus transmits a restoring force acting against the actuating direction to the end face of the control valve housing part 32 , so that the control valve housing 30 , 32 remains in its rest position. The mechanical input member 40 therefore does not change its axial position upon electromagnetic actuation of the brake booster / master cylinder unit 10 , so that a brake pedal coupled to the input member 40 , not shown here, maintains its rest position.

If the driver wants to manually intervene in the braking process and strengthen the braking during an automatic brake actuation, he can immediately increase the pressure in the first pressure chamber 48 of the master cylinder 14 by stepping on the brake pedal without having to overcome an idle travel, since this is via the actuating piston 42 adjacent first input piston 44 there is a loss-free force connection from the mechanical input member 40 to the first pressure chamber 48 . Each stroke of the input member 40 therefore immediately results in a volume displacement of hydraulic fluid in the first pressure chamber 48 .

After completion of a braking process, the hydraulic pressure in the master cylinder 14 in conjunction with the various return springs (return spring in the first pressure chamber 48 , return spring 38 in the vacuum chamber 24 , conical spring 100 in the control valve housing part 30 ) pushes the individual components of the brake booster / master cylinder unit 10 again back to the starting position according to FIG. 1.

Claims (7)

1. Brake booster / master cylinder unit ( 10 ) for a hydraulic vehicle brake system, consisting of a pneumatic brake booster ( 12 ) with an amplifier housing ( 16 ), the interior of which by at least one movable wall ( 22 ) in a vacuum chamber ( 24 ) and a working chamber ( 26 ) is subdivided into a control valve ( 28 ) along an axis (A) for controlling a pneumatic pressure difference acting on the movable wall ( 22 ), the control valve ( 28 ) having a control valve housing ( 30 , 32 ) and on the one hand by a mechanical input member ( 40 ) and independently on the other hand by an electromagnet arrangement ( 70 ), and a hydraulic master cylinder ( 14 ) coupled to the pneumatic brake booster ( 12 ) to which the actuating force introduced into the brake booster ( 12 ) and the servo force generated by it is transmitted by means of an input piston ( 44 ), de r with an actuating piston ( 42 ) which is coupled to the mechanical input member ( 40 ) and is connected to the control valve housing ( 30 , 32 ) in a force-transmitting manner and extends into a first pressure chamber ( 48 ) of the master cylinder ( 14 ), characterized in that that

• - A with respect to the control valve housing ( 30 , 32 ) telescopically displaceable auxiliary housing ( 34 ) with which the movable wall ( 22 ) is connected to transmit power,
• - A second, also up to the first pressure chamber ( 48 ) of the master cylinder ( 14 ) extending input piston ( 46 ) with the auxiliary housing ( 34 ) is connected to transmit power, and that
• - The first input piston ( 44 ) is resiliently biased towards the actuating piston ( 42 ).

2. Brake booster / master cylinder unit according to claim 1, characterized in that the first input piston ( 44 ) from the second input piston ( 46 ) is surrounded concentrically. 3. Brake booster / master cylinder unit according to claim 2, characterized in that the resilient bias of the first input piston ( 44 ) in the direction of the actuating piston ( 42 ) by a the first input piston ( 44 ) and the second input piston ( 46 ) pushing apart spring ( 50 ) is generated. 4. Brake booster / master cylinder unit according to one of claims 1 to 3, characterized in that the first input piston ( 44 ) couples in the actuating direction according to a predetermined path with the second input piston ( 46 ). 5. Brake booster / master cylinder unit according to one of the preceding claims, characterized in that the end face of the control valve housing ( 32 ) serves the first input piston ( 44 ) against the direction of actuation as a stop. 6. Brake booster / master cylinder unit according to one of the preceding claims, characterized in that the auxiliary housing ( 34 ) facing te end of the second input piston ( 46 ) is formed adjustable in length. 7. Brake booster / master cylinder unit according to claim 6, characterized in that the auxiliary housing ( 34 ) facing te end of the second input piston ( 46 ) is provided with an external thread ( 57 ) onto which an adjusting ring ( 58 ) is screwed on rests on the end face of the auxiliary housing ( 34 ).